Setting dom0-cpus to 0 doesn't use all cpus as documented

Setting dom0-cpus to 0 doesn't use all cpus as documented

[Carb, Brian A]

Hello, 

The comments for dom0-cpus in the xend-config.sxp file indicate that
setting this value to 0 in an SMP system will cause dom0 to use all the
available CPUs. However, it appears as if setting this value to 0 does
not change the number of CPUs at all.

I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on a Unisys
ES7000 with 32 CPUs and 32GB memory. In xend-config.sxp, dom0-cpus is
set to 0. When xen dom0 boots, it is using all 32 procs (as reported by
'grep processor /proc/cpuinfo | wc -l').

If I edit the xend-config.sxp file, change the value of dom0-cpus to 1,
and restart xend, dom0 correctly uses 1 CPUs. If I then change dom0-cpus
to 0 and restart xend, dom0 still uses 1 cpu. The only way to have dom0
use 32 cpus again is to either set the value of dom0-cpus to 32, or
reboot xen.

Has anyone else seen this behavior?

brian carb
unisys cmp technology lab
malvern, pa
brian.carb@unisys.com

Re: Setting dom0-cpus to 0 doesn't use all cpus as documented

[Christopher G. Stach II]

Carb, Brian A wrote:
> If I edit the xend-config.sxp file, change the value of dom0-cpus to 1,
> and restart xend, dom0 correctly uses 1 CPUs. If I then change dom0-cpus
> to 0 and restart xend, dom0 still uses 1 cpu. The only way to have dom0
> use 32 cpus again is to either set the value of dom0-cpus to 32, or
> reboot xen.
> 
> Has anyone else seen this behavior?

Try (dom0-cpus "").  I believe that's what I was using before I
dedicated one to dom0.  The comment should probably be updated, though.

-- 
Christopher G. Stach II

RE: Setting dom0-cpus to 0 doesn't use all cpus as documented

[Carb, Brian A]

Setting dom0-cpus to "" does not work either.  

brian carb (610-648-2437 or N2 385-2437)
unisys cmp technology lab
malvern, pa
brian.carb@unisys.com

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-----Original Message-----
From: Christopher G. Stach II [mailto:cgs@ldsys.net] 
Sent: Tuesday, May 09, 2006 11:07 AM
To: Carb, Brian A
Cc: Xen-devel@lists.xensource.com; Subrahmanian, Raj; Krysan, Susan;
Vessey, Bruce A; Puthiyaparambil, Aravindh
Subject: Re: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus as
documented

Carb, Brian A wrote:
> If I edit the xend-config.sxp file, change the value of dom0-cpus to 
> 1, and restart xend, dom0 correctly uses 1 CPUs. If I then change 
> dom0-cpus to 0 and restart xend, dom0 still uses 1 cpu. The only way 
> to have dom0 use 32 cpus again is to either set the value of dom0-cpus

> to 32, or reboot xen.
> 
> Has anyone else seen this behavior?

Try (dom0-cpus "").  I believe that's what I was using before I
dedicated one to dom0.  The comment should probably be updated, though.

--
Christopher G. Stach II